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The inspect module provides several useful functions to help get
information about live objects such as modules, classes, methods, functions,
tracebacks, frame objects, and code objects. For example, it can help you
examine the contents of a class, retrieve the source code of a method, extract
and format the argument list for a function, or get all the information you need
to display a detailed traceback.

There are four main kinds of services provided by this module: type checking,
getting source code, inspecting classes and functions, and examining the
interpreter stack.

The getmembers() function retrieves the members of an object such as a
class or module. The sixteen functions whose names begin with “is” are mainly
provided as convenient choices for the second argument to getmembers().
They also help you determine when you can expect to find the following special
attributes:

Return all the members of an object in a list of (name, value) pairs sorted by
name. If the optional predicate argument is supplied, only members for which
the predicate returns a true value are included.

Note

getmembers() does not return metaclass attributes when the argument
is a class (this behavior is inherited from the dir() function).

Returns a named tupleModuleInfo(name,suffix,mode,module_type)
of values that describe how Python will interpret the file identified by
path if it is a module, or None if it would not be identified as a
module. In that tuple, name is the name of the module without the name of
any enclosing package, suffix is the trailing part of the file name (which
may not be a dot-delimited extension), mode is the open() mode that
would be used ('r' or 'rb'), and module_type is an integer giving
the type of the module. module_type will have a value which can be
compared to the constants defined in the imp module; see the
documentation for that module for more information on module types.

Return the name of the module named by the file path, without including the
names of enclosing packages. This uses the same algorithm as the interpreter
uses when searching for modules. If the name cannot be matched according to the
interpreter’s rules, None is returned.

This, for example, is true of int.__add__. An object passing this test
has a __get__ attribute but not a __set__ attribute, but
beyond that the set of attributes varies. __name__ is usually
sensible, and __doc__ often is.

Methods implemented via descriptors that also pass one of the other tests
return false from the ismethoddescriptor() test, simply because the
other tests promise more – you can, e.g., count on having the
__func__ attribute (etc) when an object passes ismethod().

Data descriptors have both a __get__ and a __set__ attribute.
Examples are properties (defined in Python), getsets, and members. The
latter two are defined in C and there are more specific tests available for
those types, which is robust across Python implementations. Typically, data
descriptors will also have __name__ and __doc__ attributes
(properties, getsets, and members have both of these attributes), but this is
not guaranteed.

Return a list of source lines and starting line number for an object. The
argument may be a module, class, method, function, traceback, frame, or code
object. The source code is returned as a list of the lines corresponding to the
object and the line number indicates where in the original source file the first
line of code was found. An IOError is raised if the source code cannot
be retrieved.

Return the text of the source code for an object. The argument may be a module,
class, method, function, traceback, frame, or code object. The source code is
returned as a single string. An IOError is raised if the source code
cannot be retrieved.

Clean up indentation from docstrings that are indented to line up with blocks
of code. Any whitespace that can be uniformly removed from the second line
onwards is removed. Also, all tabs are expanded to spaces.

Arrange the given list of classes into a hierarchy of nested lists. Where a
nested list appears, it contains classes derived from the class whose entry
immediately precedes the list. Each entry is a 2-tuple containing a class and a
tuple of its base classes. If the unique argument is true, exactly one entry
appears in the returned structure for each class in the given list. Otherwise,
classes using multiple inheritance and their descendants will appear multiple
times.

Get the names and default values of a Python function’s arguments. A
named tupleArgSpec(args,varargs,keywords,defaults) is
returned. args is a list of the argument names. varargs and keywords
are the names of the * and ** arguments or None. defaults is a
tuple of default argument values or None if there are no default arguments;
if this tuple has n elements, they correspond to the last n elements
listed in args.

Deprecated since version 3.0: Use getfullargspec() instead, which provides information about
keyword-only arguments and annotations.

args is a list of the argument names. varargs and varkw are the names
of the * and ** arguments or None. defaults is an n-tuple of
the default values of the last n arguments. kwonlyargs is a list of
keyword-only argument names. kwonlydefaults is a dictionary mapping names
from kwonlyargs to defaults. annotations is a dictionary mapping argument
names to annotations.

Get information about arguments passed into a particular frame. A
named tupleArgInfo(args,varargs,keywords,locals) is
returned. args is a list of the argument names. varargs and keywords
are the names of the * and ** arguments or None. locals is the
locals dictionary of the given frame.

Format a pretty argument spec from the four values returned by
getargspec(). The format* arguments are the corresponding optional
formatting functions that are called to turn names and values into strings.

Format a pretty argument spec from the four values returned by
getargvalues(). The format* arguments are the corresponding optional
formatting functions that are called to turn names and values into strings.

Return a tuple of class cls’s base classes, including cls, in method resolution
order. No class appears more than once in this tuple. Note that the method
resolution order depends on cls’s type. Unless a very peculiar user-defined
metatype is in use, cls will be the first element of the tuple.

Bind the args and kwds to the argument names of the Python function or
method func, as if it was called with them. For bound methods, bind also the
first argument (typically named self) to the associated instance. A dict
is returned, mapping the argument names (including the names of the * and
** arguments, if any) to their values from args and kwds. In case of
invoking func incorrectly, i.e. whenever func(*args,**kwds) would raise
an exception because of incompatible signature, an exception of the same type
and the same or similar message is raised. For example:

When the following functions return “frame records,” each record is a tuple of
six items: the frame object, the filename, the line number of the current line,
the function name, a list of lines of context from the source code, and the
index of the current line within that list.

Note

Keeping references to frame objects, as found in the first element of the frame
records these functions return, can cause your program to create reference
cycles. Once a reference cycle has been created, the lifespan of all objects
which can be accessed from the objects which form the cycle can become much
longer even if Python’s optional cycle detector is enabled. If such cycles must
be created, it is important to ensure they are explicitly broken to avoid the
delayed destruction of objects and increased memory consumption which occurs.

Though the cycle detector will catch these, destruction of the frames (and local
variables) can be made deterministic by removing the cycle in a
finally clause. This is also important if the cycle detector was
disabled when Python was compiled or using gc.disable(). For example:

defhandle_stackframe_without_leak():frame=inspect.currentframe()try:# do something with the framefinally:delframe

The optional context argument supported by most of these functions specifies
the number of lines of context to return, which are centered around the current
line.

Get a list of frame records for a frame and all outer frames. These frames
represent the calls that lead to the creation of frame. The first entry in the
returned list represents frame; the last entry represents the outermost call
on frame‘s stack.

Get a list of frame records for a traceback’s frame and all inner frames. These
frames represent calls made as a consequence of frame. The first entry in the
list represents traceback; the last entry represents where the exception was
raised.

CPython implementation detail: This function relies on Python stack frame support in the interpreter,
which isn’t guaranteed to exist in all implementations of Python. If
running in an implementation without Python stack frame support this
function returns None.

Return a list of frame records for the stack between the current frame and the
frame in which an exception currently being handled was raised in. The first
entry in the list represents the caller; the last entry represents where the
exception was raised.

For cases where you want passive introspection, like documentation tools, this
can be inconvenient. getattr_static() has the same signature as getattr()
but avoids executing code when it fetches attributes.

Note: this function may not be able to retrieve all attributes
that getattr can fetch (like dynamically created attributes)
and may find attributes that getattr can’t (like descriptors
that raise AttributeError). It can also return descriptors objects
instead of instance members.

If the instance __dict__ is shadowed by another member (for example a
property) then this function will be unable to find instance members.

New in version 3.2.

getattr_static() does not resolve descriptors, for example slot descriptors or
getset descriptors on objects implemented in C. The descriptor object
is returned instead of the underlying attribute.

You can handle these with code like the following. Note that
for arbitrary getset descriptors invoking these may trigger
code execution:

# example code for resolving the builtin descriptor typesclass_foo:__slots__=['foo']slot_descriptor=type(_foo.foo)getset_descriptor=type(type(open(__file__)).name)wrapper_descriptor=type(str.__dict__['__add__'])descriptor_types=(slot_descriptor,getset_descriptor,wrapper_descriptor)result=getattr_static(some_object,'foo')iftype(result)indescriptor_types:try:result=result.__get__()exceptAttributeError:# descriptors can raise AttributeError to# indicate there is no underlying value# in which case the descriptor itself will# have to dopass

When implementing coroutine schedulers and for other advanced uses of
generators, it is useful to determine whether a generator is currently
executing, is waiting to start or resume or execution, or has already
terminated. getgeneratorstate() allows the current state of a
generator to be determined easily.